Colonic SCFA Uptake: pH-Dependent Transport Across the Gut Epithelium

Gut bacteria ferment dietary fibre into short-chain fatty acids such as butyrate, propionate and acetate — but getting those molecules out of the colonic lumen and into the body depends on chemistry, not just production. This simulator renders a 3D cross-section of the colonic epithelium and tracks individual SCFA molecules as they either diffuse passively through the membrane in their protonated (neutral) form, or queue for a saturable MCT1 transporter when ionized, exactly as governed by the Henderson–Hasselbalch equilibrium and Michaelis–Menten carrier kinetics. Adjust luminal pH, SCFA concentration and transporter density to see how the two absorption pathways trade off, with live readouts for ionization fraction, passive flux, transporter flux and carrier saturation.